Examine source code of up-to-eleven

{
  "description": "Increase the volume of audio on a tab, making quiet sounds lounder and limiting loud sounds.",
  "manifest_version": 2,
  "name": "up-to-eleven",
  "version": "0.3resigned1",
  "background": {
    "scripts": [
      "up-to-eleven.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "48": "icons/uptoeleven-disabled.png",
      "96": "icons/uptoeleven@2x-disabled.png"
    }
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{242c2018-6cd5-4c97-ac19-3f248ccb8272}"
    }
  }
}